Adjustable-angle spinal fixation element

ABSTRACT

A spinal fixation device is provided having first and second elongate members that are angularly adjustable relative to one another. Each elongate member can include a connecting feature formed on a terminal end thereof, and each connecting feature can be coupled to one another to allow angular movement of the first and second elongate members. The device can also include a locking mechanism that is adapted to couple to the connecting feature on each of the first and second elongate members to lock the elongate members in a fixed position relative to one another.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/708,919 filed on Mar. 31, 2004 and entitled “Adjustable-Angle SpinalFixation Element,” which is hereby incorporated by reference in itsentirety.

FIELD OF THE INVENTION

The present application relates to devices for use in spinal surgery,and in particular to spinal fixation devices having an adjustable angle.

BACKGROUND OF THE INVENTION

Stabilization of the spine is often required following trauma, tumor, ordegenerative pathologies. Although each region of the spine presentsunique clinical challenges, posterior fixation of the cervical spine isparticularly challenging. The anatomy of the cervical spine makes it atechnically challenging area to instrument. Specifically, several vitalneural and vascular structures, including the vertebral arteries, nerveroots, and spinal cord, must be avoided during surgery.

Current methods of posterior cervical stabilization include the use ofan occipital spinal plate and a transition rod for fixation of thecervico-thoracic junction. Such devices typically include a spinalfixation element, such as a relatively rigid fixation rod, that iscoupled to adjacent vertebrae by attaching the element to variousanchoring devices, such as hooks, bolts, wires, or screws. Often tworods are disposed on opposite sides of the spinous process in asubstantially parallel relationship. The fixation rods can have apredetermined contour that has been designed according to the propertiesof the target implantation site, and once installed, the rods hold thevertebrae in a desired spatial relationship, either until healing orspinal fusion has taken place, or for some longer period of time.

It is often the case that the predetermined contour of a fixation roddoes not exactly fit the contour of the implantation site. This may beattributed to various factors including a patients age, which directlyrelates to the size of their spinous process, irregular contouring dueto disease or injury, or malformation due to a birth defect. Theseconditions often make it impossible to use a pre-contoured fixation rod.In these cases, multiple rods projecting at multiple angles are used,however such devices can complicate the surgery, as well as therecovery, and they can add undue strain on the spinous process, possiblyresulting in an unsuccessful repair of the spine.

Accordingly, there presently exists a need for improved spinal fixationdevices that can be easily installed and that allow for angularadjustment and subsequent locking. There is also a need for spinalfixation devices that have a low-profile to avoid potential irritationand injury to the patient.

SUMMARY OF THE INVENTION

The present invention generally provides a spinal fixation device havingfirst and second elongate members that are angularly adjustable relativeto one another. Each elongate member can include a connecting featureformed on a terminal end thereof, and each connecting feature can becoupled to one another to allow angular movement of the first and secondelongate members. The device can also include a locking mechanism thatis adapted to couple to the connecting feature on each of the first andsecond elongate members to lock the elongate members in a fixed positionrelative to one another.

In one embodiment, the connecting feature on the first elongate memberis a female connector, and the connecting feature on the second elongatemember is a male connector that is adapted to receive the femaleconnector. The female connector preferably includes opposed armsdefining a recess therebetween for receiving the male connector. A borecan extend through the opposed arms on the female connector and throughthe male connector for receiving a central mating element that isadapted to mate the male and female connectors to one another. In anexemplary embodiment, the central mating element is a cylindrical memberthat is adapted to allow at least one of the first and second elongatemembers to rotate thereabout. More preferably, however, the cylindricalmember is fixedly coupled to a portion of the female connector, and themale connector is free to rotate about the cylindrical member.

In use, the locking mechanism can engage the cylindrical member toprevent movement of the male connector relative to the female connector.While a variety of locking mechanisms can be used, in one embodiment thelocking mechanism can be in the form of a slot extending through themale connector such that the male connector is in the form of a clamp,and the locking mechanism can also include a fastening element that isadapted to engage the male connector to clamp the cylindrical memberwithin the bore. The fastening element is preferably a threaded member.

In other aspects of the present invention, the connecting feature oneach of the first and second elongate members can rotate about a centralaxis extending substantially perpendicular to an axis of each first andsecond elongate members. More preferably, each connecting feature caninclude opposed inner and outer surfaces, and the inner surface on eachconnecting feature can be in contact one another. In an exemplaryembodiment, the inner surface on each connecting feature is adapted toprevent rotation of the first and second elongate members relative toone another when the locking mechanism is in a locked configuration. Theconnecting features can also optionally include anti-rotation features,such as gear teeth, formed on the inner surface of each connectingfeature.

In further aspects, a first bore can extend through the inner and outersurface of the connecting feature on the first elongate member and asecond bore extending through the inner and outer surface of theconnecting feature on the second elongate member. In one embodiment, thebores can be adapted to receiving the locking mechanism, which can be,for example, a fastening element having a head and a shaft with threadsformed thereon. The first bore is preferably non-threaded for freelyrotatably receiving a portion of the shaft of the fastening element, andthe second bore is preferably threaded for mating with the threadsformed on the shaft of the locking mechanism.

In an alternative embodiment, a pin member can be disposed through thefirst and second bores extending through the inner and outer surfaces ofthe connecting feature, and the pin member can include a transverse boreextending therethrough for receiving at least a portion of the lockingmechanism. A receiving bore can be formed in at least one connectingfeature, and the receiving bore can be in communication with the centralbore to allow the locking mechanism to extend therethrough and into thetransverse bore in the pin member. In a further embodiment, the lockingmechanism can be adapted to engage the pin member to translate the firstand second connecting features toward one another to lock the first andsecond elongate members in a fixed position relative to one another.

In yet another embodiment of the present invention, the connectingfeature on each of the first and second elongate members can be slidablycoupled to one another. More preferably, the connecting feature on eachof the first and second elongate members is a substantially curvedterminal portion, and the terminal portion are complementary forslidably mating to one another. Each terminal portion can include a slotformed therein for receiving the locking mechanism. Each terminalportion can also include one or more anti-sliding surface featuresformed on a portion thereof to prevent movement of the first and secondelongate members relative to one another when the locking mechanism isin a locked configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is an exploded view of one embodiment of an adjustable-anglespinal fixation device having male and female connecting featuresaccording to the present invention;

FIG. 1B is a side, assembled view of the adjustable-angle spinalfixation device shown in FIG. 1A in a locked position;

FIG. 1C is a perspective view of a central mating element of theadjustable-angle spinal fixation device shown in FIG. 1A;

FIG. 1D is an enlarged perspective view of a male connector of theadjustable-angle spinal fixation device shown in FIG. 1A;

FIG. 1E is an exploded view of another embodiment of an adjustable-anglespinal fixation device having a spinal fixation plate with a maleconnecting feature and a spinal rod with a female connecting feature formating to the male connecting feature;

FIG. 2A is an exploded view of another embodiment of an adjustable-anglespinal fixation device according to the present invention havinganti-rotation features formed thereon;

FIG. 2B is an enlarged side view of the adjustable-angle spinal fixationdevice shown in FIG. 2A in a locked position;

FIG. 3A is an exploded view of an adjustable-angle spinal fixationdevice having a pin member for receiving a fastening element accordingto yet another embodiment the present invention;

FIG. 3B is a perspective view of the adjustable-angle spinal fixationdevice shown in FIG. 3A in a locked position;

FIG. 4A is a perspective view of yet another embodiment of anadjustable-angle spinal fixation device according to the presentinvention having substantially curved complimentary matable connectingfeatures;

FIG. 4B is a side view of the adjustable-angle spinal fixation deviceshown in FIG. 4A in a locked position;

FIG. 5A is a side view of another embodiment of an adjustable-anglespinal fixation device according to the present invention having alocking mechanism that provides a polyaxial connection with first andsecond spinal fixation elements coupled thereto;

FIG. 5B is a top perspective view of the adjustable-angle spinalfixation device shown in FIG. 5B in a locked position; and

FIG. 5C is a bottom perspective view of the adjustable-angle spinalfixation element shown in FIG. 5A in a locked position.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides various angularly-adjustable spinalfixation devices, each of which generally includes first and secondelongate members 12 a, 12 b, a connecting feature 20 formed on aterminal end of each of the first and second elongate members 12 a, 12b, and a locking mechanism 30 that is adapted to lock the first andsecond elongate members 12 a, 12 b in a fixed position relative to oneanother. The elongate members 12 a, 12 b are preferably spinal rodsand/or plates that are used, for example, in the stabilization of thespine following trauma, tumor, or degenerative pathologies. Among manyother advantages, the devices are particularly useful to allow a spinalrod to be positioned and locked in a desired angular orientation withoutthe need to reshape the rod, and without requiring the point ofadjustment to be attached to the spine of a patient.

FIGS. 1A-1B illustrate one exemplary embodiment of a spinal fixationdevice 10 having first and second elongate members 12 a, 12 b, aconnecting feature 20 a, 20 b formed on a terminal end 14, 16 of each ofthe first and second elongate members 12 a, 12 b, and a lockingmechanism 30 that is adapted to lock the first and second elongatemembers 12 a, 12 b in a fixed position relative to one another. In use,the first and second elongate members 12 a, 12 b can be angularlyadjusted relative to one another and, once properly positioned, they canbe locked in a fixed position relative to one another using the lockingmechanism 30.

The first and second elongate members 12 a, 12 b can each have any shapeor size, and each elongate member 12 a, 12 b can vary in diameterrelative to one another. The elongate members 12 a, 12 b can also varyin length depending on the intended use. In the illustrated embodiment,the first and second elongate members 12 a, 12 b are substantiallycylindrical spinal rods, each having a terminal end 13, 15 that isadapted to mate to a spinal anchor, such as a hook, screw, bolt, plate,etc. The opposed terminal end 14, 16 of each elongate member 12 a, 12 bincludes the connecting feature 20 a, 20 b formed thereon and mated toone another.

While the terminal ends 13, 15 of the elongate members 12 a, 12 b shownin FIGS. 1A-1B extend along the axis of the elongate members 12 a, 12 b,the terminal ends 13, 15 can extend at an angle relative to the elongatemembers 12, 12 b. For example, as shown in FIG. 1E, the terminal end 13′of one of the elongate members, e.g., the first elongate member 12 a′,can extend at a 90° angle relative to the longitudinal axis of thesecond elongate member 12 b, as shown in FIG. 1E. In other embodiments,one or both of the elongate members can be in the form of a spinalfixation plate. For example, as shown in FIG. 1E, the second elongatemember 12 b is in the form of a spinal fixation plate 12 b′, rather thana spinal rod.

Continuing to refer to FIGS. 1A-1B, each connecting feature 20 a, 20 bcan have a variety of configurations, but they should be adapted toallow for angular adjustability of the first and second elongate members12 a, 12 b relative to one another. In the embodiment shown in FIGS.1A-1B, the connecting feature 20 a on the first elongate member 12 a isin the form of a female connector, and the connecting feature 20 b onthe second elongate member 12 is in the form of a male connector. Theterminal ends 14, 16 of the elongate members 12 a, 12 b can mate to theconnectors 20 a, 20 b at any location, but in an exemplary embodimentthe elongate members 12 a, 12 b are positioned such that the connectors20 a, 20 b do not interfere with the patient's spinal anatomy.

While the male and female connectors 20 a, 20 b can have a variety ofconfigurations, in an exemplary embodiment the female connector 20 a hasopposed arms 23 a, 23 b that are spaced a distance apart from oneanother to form an open recess 26 therebetween for seating the maleconnector 20 b. Each arm 23 a, 23 b can vary in shape and size, but inan exemplary embodiment, as shown, the arms 23 a, 23 b each have asubstantially circular shape. The male connector 20 b can also vary inshape and size, but it preferably has a shape that corresponds to thefemale connector 22, and more preferably the male connector 20 b issubstantially circular.

Each connector member 20 a, 20 b also preferably includes a central bore28 a, 28 b that extends therethrough in a direction that issubstantially perpendicular to a longitudinal axis L₁, L₂ each of thefirst and second elongate members 12 a, 12 b. The central bore 28 a, 28b is adapted to receive a central mating element 29 therethrough formating the connectors 20 a, 20 b, and for allowing one or bothconnectors 20 a, 20 b to rotate thereabout. The central mating element29 can have a variety of configurations, however FIG. 1C illustrates acentral mating element 29 having a substantially cylindrical shape andincluding proximal and distal ends 29 c, 29 d. In a preferredembodiment, one of the connectors, e.g., the female connector 20 a, isconfigured to receive the mating element 29 such that the femaleconnector 20 a and the mating element 29 are in a fixed positionrelative to one another, and the male connector 20 b is free to rotateabout the mating element 29 and relative to the female connector 20 a.This can be achieved, for example, by providing complementary featureson the mating element 29 and the female connector 20 a to preventrotation relative to one another. As shown in FIGS. 1A-1C, the portionof the bore 28 a that extends through the first arm 23 a has asubstantially square shape, and the distal end 29 d of the centralmating element 29 includes a substantially square-shaped protrusion 29 aformed thereon and adapted to be disposed within the corresponding bore28 a formed in the female connector 20 a. As a result, when the device10 is in use, the female connector 20 a is locked in a fixed positionrelative to the mating element 29, but the male connector 20 b is freeto rotate thereabout. A person skilled in the art will appreciate thatthe complementary features on the mating element 29 and the femaleconnector 20 a can have a variety of other configurations and by way ofnon-limiting example, the complementary mating features can have ahexagonal shape, an octagonal shape, a D-shape, or any other shape thatprevents rotation of the female connector 20 a relative to the matingelement 29. In other embodiments, the mating element 29 and the femaleconnector 20 a can be fixedly mated to one another, for example, bywelding the components together, to prevent rotation of the femaleconnector 20 a relative to the mating element 29.

As previously stated, the device 10 also includes a locking mechanism 30that is adapted to lock the first and second elongate members 12 a, 12 bin a fixed position relative to one another. While virtually anytechnique can be used to lock the elongate members 12 a, 12 b in a fixedposition, FIGS. 1A, 1B, and 1D illustrate an exemplary embodiment of alocking mechanism 30. In this embodiment, the male connector 20 b is inthe form of a clamp mechanism and more particularly it includes a slot25 extending therethrough and in communication with the central bore 28formed therein, as shown in more detail in FIG. 1D. The slot 25separates the male connector 20 b into upper and lower portions 24 a, 24b that are movable between an open position and a closed position inwhich the male connector 20 b is adapted to engage the mating element 29extending through the central bore 28 b.

In order to move the upper and lower portions 24 a, 24 b to the closedposition, the male connector 24 can include a receiving bore 28 c formedtherein and extending through the upper and lower portions 24 a, 24 b.The receiving bore 28 c is adapted to receive a fastening element 27that is effective to pull one or both of the upper and lower portions 24a, 24 b toward one another to close the slot 25. As a result, thecentral bore 28 b extending through the male connector 20 b is decreasedin size, thereby allowing the male connector 20 b to engage the matingelement 29 and preventing rotation of the second elongate member 12 brelative to the first elongate member 12 a.

The fastening element 27 that is disposed through the receiving bore 28c can have a variety of configurations, and it can be, for example, ascrew, anchor, or bolt. In the illustrated embodiment, as shown in FIG.1A, the fastening element 27 is a threaded member, e.g., a screw, havinga head 27 a and a thread shank 27 b. The receiving bore 28 c formed inthe male connector 20 b can thus includes threads formed therein formating with the threaded shank 27 b on the fastening element 27. Morepreferably, however, the portion of the receiving bore 28 c formed inthe upper portion 24 a of the male connector 20 b is non-threaded toallow free rotation of the threaded member 27 with respect thereto, andthe portion of the receiving bore 28 c formed in the lower portion 24 bof the male connector 20 b is threaded to mate with the threaded shank27 b. This allows the fastening element 27 to pull the upper portion 24a toward the lower portion 24 b, thereby locking the portions 24 a, 24 brelative to one another and locking the male connector 20 b relative tothe mating element 29.

Those skilled in the art will appreciate that the receiving bore 28 band male connector 20 b can be a variety of other configurations tofacilitate locking of the male connector 20 b. By way of non-limitingexample, the central mating element 29 and/or an inner surface of thebore 28 b on the male connector 20 b can have anti-rotation featuresformed thereon, such that when the male connector 20 b is closed theanti-rotation features can assist in securing the male connector 20 baround the central mating element 29. The anti-rotation features can be,for example, a non-slip coating applied to the surface of the matingelement 29 and/or the bore 28 b, teeth or knurling formed on the surfaceof the mating element 29 and/or the bore 28 b, or other grippingfeatures known to one skilled in the art.

In use, the fastening element 27 can be partially threaded into the bore28 c formed in the male connector 20 b to allow the first and secondelongate members 12 a, 12 b to rotate relative to one another. Althoughthe elongate members 12 a, 12 b can be adapted for multi-axial rotation,in the illustrated embodiment the elongate members 12 a, 12 b rotatealong a single plane. Each elongate member 12 a, 12 b may be configuredto rotate such that a complementary angle α_(c) between the elongatemembers 12 a, 12 b, as shown in FIG. 1B, can range from about 0° to 135°in each direction from a coaxial position, and more preferably fromabout 60° to 135° in each direction from a coaxial position. Once theelongate members 12 a, 12 b are in a desired position relative to oneanother, which is typically as a result of attaching the terminals ends13, 15 of the elongate members 12 a, 12 b to an anchoring device, thefastening element 27 can be fully threaded into the bore 28 c in themale connector 20 b to cause the male connector 20 b to engage themating element 29, thereby preventing rotation of the second elongatemember 12 b relative to the first elongate member 12 a.

FIGS. 2A-2B illustrate another embodiment of a spinal fixation device100 according to the present invention. In this embodiment, the spinalfixation device 100 includes a first elongate member 112 a having afirst connecting feature 120 a formed thereon that is matable to asecond connecting feature 120 b formed on a second elongate member 112b. Each connecting feature 120 a, 120 b can have any shape and size, butin the illustrated embodiment the connecting features 120 a, 120 b havea substantially circular shape. Each connecting feature 120 a, 120 balso includes opposed inner and outer surfaces 114 a, 114 b, 116 a, 116b, and the inner surface 114 a, 116 a of each connecting feature 120 a,120 b is adapted to be positioned adjacent to one another. As a result,the elongate members 112 a, 112 b are offset from each other in adirection parallel to a plane of rotation. While not shown, one or bothelongate members 112 a, 112 b can optionally be angled at anyorientation relative to the plane of rotation, such that the elongatemember(s) 112 a, 112 b intersects the plane of rotation.

Continuing to refer to FIGS. 2A-2B, the connecting features 120 a, 120 balso each include a central bore 122 a, 122 b extending through theinner and outer surfaces 114 a, 114 b, 116 a, 116 b thereof and adaptedto receiving a locking mechanism 127. The locking mechanism 127, whendisposed through the central bores 112 a, 112 b, allows the connectors120 a, 120 b, and consequently the first and second elongate members 112a, 112 b, to rotate there around. In an exemplary embodiment, eachelongate member 112 a, 112 b can rotate 360° relative to one another.One skilled in the art will appreciate that certain applications mayrequire a range of rotation of less than 360°, in which case arestriction, such as a mechanical stop, may be introduced to limit therange of rotation.

The locking mechanism 127 can have a variety of configurations, but inan exemplary embodiment, as shown, the locking mechanism 127 is athreaded member, e.g., a screw, that is similar to threaded member 27shown in FIGS. 1A-1D. The central bore 122 b in the first elongatemember 120 a can be configured to freely, rotatably receive thefastening element 127, and the central bore 122 a in the second elongatemember 120 b can be threaded to mate with the threaded shank 127 b ofthe fastening element 127. In use, when the fastening element 127 is inan unlocked position, it allows the first and second elongate members112 a, 112 b to freely rotate relative to one another. Once properlypositioned, the fastening element 127 can be fully threaded into thecentral bore 122 b in the second elongate member 120 b, as shown in FIG.2B, to lock the connectors 120 a, 120 b in a fixed position relative toone another, thereby preventing rotation of the first and secondelongate members 112 a, 112 b.

The configuration of the locking mechanism 127 on spinal fixation device100 is particularly advantageous for use in lumbar or sacral-pelvicfixation. In particular, the fastening element 127 extends through theconnecting features 120 a, 120 b in a direction that is substantiallyperpendicular to the plane of rotation of the elongate members 112 a,112 b, thus allowing an insertion tool, such as a driver tool, to beused to thread the fastening element 127 into the connecting features120 a, 120 b when the device 100 is implanted.

In a further embodiment, the inner surface 114 a, 116 a of eachconnector 120 a, 120 b can optionally include one or more anti-rotationfeatures formed thereon. The anti-rotation features are effective tofacilitate locking of the first and second elongate members 112 a, 112 bin a fixed position relative to one another. While various anti-rotationfeatures can be used, each connector 120 a, 120 b can include gear teeth118 a, 118 b formed thereon for engaging one another when the lockingmechanism 127 is fully locked relative to the connectors 120 a, 120 b.In an exemplary embodiment, the gear teeth 118 a, 118 b have a size thatallows angular positioning of the first and second elongate members 112a, 112 b in 4° increments relative to one another, however any incrementcan be used.

FIGS. 3A-3B illustrate yet another embodiment of a spinal fixationdevice 100′ in accordance with the present invention. The device 100′ issimilar to the device 100 shown in FIGS. 2A-2B, and thus like referencenumbers are used to refer to like parts. In this embodiment, the lockingmechanism differs in that it includes a pin member 127′, rather than athreaded member 127, that extends through the central bore 122 a, 122 bin each connector 120 a, 120 b. The locking mechanism also includes afastening element 130 that is adapted to at least partially extend intothe pin member 127′ to lock the connectors 120 a, 120 b in a fixedposition. The orientation of the pin member 127′ is particularlyadvantageous for use in occipital-cervical fixation since the pin member127′ extends through the connecting features 120 a, 120 b in a directionthat is substantially parallel to the plane of rotation of the elongatemembers 112 a, 112 b.

The pin member 127′ can have a variety of shapes and sizes, but in anexemplary embodiment it has head 127 a′ and a shank 127 b′ having asubstantially cylindrical shape to allow the connector members 120 a′,120 b′ to rotate there around. The head 127 a′ of the pin member 127′ isconfigured to sit within a recess 132′ formed within an opening of thecentral bore 122 a′ extending through the first connector 120 a′. Theshank 127 b′ of the pin member 127′ is configured to extend through andsit within the bore 122 a′, 122 b′ in each connector 120 a′, 120 b′, andit includes a transverse bore 128′ formed therein for receiving aportion of a fastening element 130′.

The fastening element 130′ preferably includes a proximal threaded shank131 a′ that is adapted to mate with a threaded receiving bore 132′formed in the second connector 120 b′, and a distal non-threaded shank131 b′ that is adapted to extend into the transverse bore 128′ formed inthe pin member 127′. In use, the fastening element 130′ can be partiallythreaded into the threaded bore 132′ formed in the second connector 120b′ to allow rotation of the first and second elongate members 112 a′,112 b′ relative to one another. In this position, the non-threaded shank131 b′ on the fastening element 130′ extends into the transverse bore128′ in the pin member 127′, and it preferably loosely engages the bore128′ to allow rotation between the first connector 120 a′ and the secondconnector 120 b′. Further threading of the fastening element 130′ intothe threaded bore 132′ will lock the angular position of the first andsecond elongate members 112 a′, 112 b′ relative to one another, as shownin FIG. 3B. While various techniques can be used to lock the first andsecond elongate members 112 a′, 112 b′ relative to one another, in oneembodiment the this can be achieved by forming the transverse bore 128′in the pin member 127′ at a location that is axially offset from thereceiving bore 132′ in the second connector 120 b′ when the pin member127′ is fully disposed therein. Thus, upon further rotation of thefastening element 130′ into the receiving bore 132′, the non-threadedshank 131 b′ causes the first connector 120 a′ to translate furthertoward the second connector 120 b′, thereby locking the connectors 120a′, 120 b′ in a fixed position relative to one another. In this fixedposition, the head of 127 a′ of the pin member 127′ is preferably fullyseated within the recess 132′ formed in the bore 122 a′ of the firstconnector 120 a′. In other embodiments, the transverse bore 128′ and thenon-threaded shank 131 b′ can contain features to translation and/orlocking of the connectors 120 a′, 120 b′. For example, a portion of theshank 131 b′, e.g., a distal end, and a portion of the transverse bore128′, e.g., an opening, can include conforming chamfers formed thereon.

As previously described with respect to connector 100 shown in FIGS.2A-2B, an inner surface of each connector 120 a′, 120 b′ can includeanti-rotation features formed therein, such as gear teeth or knurling toprevent rotation of the first and second elongate members 112 a′, 112 b′relative to one another when the device 100′ is in the lockedconfiguration.

FIGS. 4A-4B illustrate yet another embodiment of a spinal fixationdevice 400 in accordance with the present invention. In this embodiment,the connecting features 420 a, 420 b on the first and second elongatemembers 412 a, 412 b each have a substantially elongate, curvedconfiguration such that they include complimentary matable surfaces 470,472. One of the connecting features, e.g., the first connecting feature420 a, can include an elongate slot or opening 422 a formed therein, andthe other connecting feature, e.g., the second connecting feature 420 b,can include a threaded bore 422 b formed therein. The slot 422 a andbore 422 b are configured to receive a locking mechanism 430 that iseffective to lock the first elongate member 420 a in a fixed positionrelative to the second elongate member 420 b. In an exemplaryembodiment, the locking mechanism 430 includes threaded member 432 thatcan be disposed through the slot 422 a in the first elongate member 420a, and that is matable with the threaded bore 422 b in the secondelongate member 420 b.

In use, when the fastening element 432 is partially threaded into thethreaded bore 422 b, the first and second connectors 420 a, 420 b areslidably movable relative to one another, thereby adjusting the angle ofthe first and second elongate members 412 a, 412 b relative to oneanother. The radius of curvature can vary depending on the curvature ofeach connector 420 a, 420 b. Once properly positioned, the fasteningelement 432 can be fully threaded into the bore 422 b to lock theelongate members 412 a, 412 b in a fixed position and at a fixed angle.A person skilled in the art will appreciate that the locking mechanismcan be a rivet, pin, bolt or other fastening device known in the art.

In a further embodiment, the complimentary matable surfaces 470, 472 caninclude gear teeth formed thereon and adapted to prevent slipping orrotation when the locking mechanism 430 is in a locked position. While avariety of anti-slip features can be formed on the complimentary matablesurfaces 470, 472, FIGS. 4A and 4B illustrate gear teeth (only gearteeth 480 on the second connecting feature 420 b are shown) formedthereon.

FIG. 5A illustrates another exemplary embodiment of a spinal fixationdevice 500 according to the present invention. In general, theconnecting feature 520 a, 520 b on each elongate member 512 a, 512 b isin the form of a protrusion that allows polyaxial movement of theelongate members 512 a, 512 b relative to the locking mechanism 530.While the shape of the protrusion 520 a, 520 b can vary, in theillustrated embodiment the each protrusion 520 a, 520 b has a generallybulbous shape. The locking mechanism 530 includes a housing 510 that isadapted to receive the protrusion 520 a, 520 b of each elongate member512 a, 512 b such that the first and second elongate members 512 a, 512b are substantially opposed to one another. Additionally, the lockingmechanism 530 is adapted to lock the first and second elongate members512 a, 512 b in a fixed position relative to one another, as shown inFIGS. 5B and 5C.

The housing 510 of the locking mechanism 530 can have a variety ofshapes and sizes, but in the illustrate embodiment, the housing 510 hasa substantially rectangular shape and it includes a central opening 585formed therein and extending between opposed top and bottom surfaces581, 582 thereof. Additionally, the housing 510 has at least two opposedside openings 583 a, 583 b, shown in FIG. 5A, extending from opposedfirst and second side surfaces 587, 588 thereof. Each elongate member512 a, 512 b is positioned through the first and second opposed sideopenings 583 a, 583 b such that the bulbous protrusion 520 a, 520 bformed thereon is seated within the central opening 585 of the housing510. Preferably, each of the first and second opposed side openings 583a, 583 b in the housing 510 are sized to have a diameter d₁ that issmaller than a diameter d₂ of the bulbous protrusion 520 a, 520 b oneach elongate member 512 a, 512 b to prevent the bulbous protrusions 520a, 520 b from passing therethrough. The diameter d₁ of the opposed sideopenings 583 a, 583 b should, however, be larger than the diameter dr ofeach elongate member 512 a, 512 b to allow the elongate members 512 a,512 b to extend therethrough and to rotate freely. In an exemplaryembodiment, the side openings 583 a, 583 b allow the first and secondelongate members 512 a, 512 b to rotate about 60° in all directionsrelative to the housing 510, and more preferably to rotate in the rangeof about 30° to 60°. As a result, the first and second elongate members512 a, 512 b can form an angle in the range of about 0 to 120° relativeto one another.

As previously stated, the locking mechanism 530 is also adapted to lockthe elongate members 512 a, 512 b in a fixed position relative to oneanother. While various techniques can be used to lock the elongatemembers 512 a, 512 b in a fixed position, in the illustrated embodimentthe locking mechanism 530 includes a fastening element 590, which can bea screw, rivet, bolt or other fastening device known in the art, that isadapted to mate to a receiver member 592. In the illustrated embodiment,the fastening member 590 is a threaded member having a threaded shank590 a that is adapted to extend through the central opening 585 to matewith the receiving member 592, and a head 590 b that is adapted to restagainst or sit within a portion of the central opening 585 formed in thetop surface 581 of the housing.

The receiver member 592 is preferably positioned within a portion of thecentral opening 585 that is adjacent to the bottom surface 582 of thehousing 510, and it has a shape that is effective to lock the bulbousprotrusion 520 a, 520 b on each elongate member 512 a, 512 b in a fixedposition within the central opening 585 when the fastening element 590is mated thereto. In particular, the receiving member 592 can have asubstantially rectangular shape, as shown in FIG. 5C, and it can includeopposed concave side surfaces 592 a, 592 b formed thereon. In use, thefastening element 590 can be threaded into a corresponding threaded bore592 c extending through the receiving element 592 to engage thereceiving element 592 and pull it into the central bore 585 formed inthe housing 510. As the receiving element 592 moves into the centralbore 585, the opposed side surfaces 592 a, 592 b abut against thebulbous protrusion 520 a, 520 b on each elongate member 512 a, 512 b tolock the protrusions 520 a, 520 b in a fixed position relative to thehousing 510.

A person skilled in the art will appreciate that the configuration ofthe protrusion 520 a, 520 b on each elongate member 512 a, 512 b and thereceiving element 592 can vary. For example, each connecting features520 a, 520 b can have a substantially concave recess formed therein, andthe receiving element 592 can include convex side surfaces formedthereon for engaging the connecting features 520 a, 520 b.

It is possible that some applications will require angular adjustabilityof only one of the elongate members. Accordingly, in each of the variousembodiments of the present invention, one of the elongate members can beangularly adjustable and the other elongate member can maintained in afixed position.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

1. A spinal fixation device, comprising: first and second elongatemembers coupled to one another such that the first and second elongatemembers are angularly adjustable relative to one another, whereinangular adjustment of the first elongate member is limited to a firstplane and angular adjustment of the second elongate member is limited toa second plane that is parallel to the first plane; and a lockingmechanism adapted to lock the elongate members in a fixed positionrelative to one another independent of a bone anchor.
 2. The spinalfixation device of claim 1, wherein the first and second elongatemembers are angularly adjustable along a single plane 360° relative toone another.
 3. The spinal fixation device of claim 1, wherein the firstand second elongate members each comprise a spinal fixation rod.
 4. Thespinal fixation device of claim 1, further comprising a connectingfeature formed on a terminal end of each of the first and secondelongate members for coupling the first and second elongate members toone another, and for allowing angularly adjustability of the elongatemembers.
 5. The spinal fixation device of claim 4, wherein eachconnecting feature includes opposed inner and outer surfaces, andwherein the inner surface on each connecting feature is in contact oneanother.
 6. The spinal fixation device of claim 5, wherein the innersurface on each connecting feature is adapted to prevent rotation of thefirst and second elongate members relative to one another when thelocking mechanism is in a locked configuration.
 7. The spinal fixationdevice of claim 5, further comprising anti-rotation features formed onthe inner surface of each connecting feature.
 8. The spinal fixationdevice of claim 7, wherein the anti-rotation features comprise gearteeth formed on the inner surface of each connecting feature.
 9. Thespinal fixation device of claim 7, wherein the anti-rotation feature isadapted to allow each connecting feature to rotate in incrementsrelative to one another.
 10. The spinal fixation device of claim 4,further comprising a pin member adapted to removably couple the firstand second connecting features.
 11. The spinal fixation device of claim10, wherein the locking mechanism is adapted to engage the pin member totranslate the first and second connecting features toward one another tolock the first and second elongate members in a fixed position relativeto one another.
 12. The spinal fixation device of claim 11, wherein oneof the first and second connecting features includes a receiving boreformed therein for receiving the locking mechanism.
 13. The spinalfixation device of claim 12, wherein the receiving bore is threaded formating with corresponding threads formed on the locking mechanism.
 14. Aspinal fixation device, comprising: first and second elongate memberscoupled to one another such that the first and second elongate membersare angularly adjustable relative to one another, the angularadjustability of each elongate member being limited to a single plane; apin member adapted to removably couple the first and second elongatemembers, the pin member extending along an axis that extends transverseto the single plane of angular adjustability of each elongate member;and a locking mechanism adapted to lock the elongate members in a fixedposition relative to one another, the locking mechanism extending alongan axis that is substantially parallel to the single plane of angularadjustability of each elongate member.
 15. The spinal fixation device ofclaim 14, wherein the pin member extends along an axis that extendssubstantially perpendicular to the single plane of angular adjustabilityof each elongate member.
 16. The spinal fixation device of claim 14,wherein the pin member is adapted to translate at least one of the firstand second elongate members toward the other one of the first and secondelongate members.
 17. The spinal fixation device of claim 14, whereinthe locking mechanism is adapted to engage the pin member.
 18. A spinalfixation device, comprising: a first spinal fixation rod having a firstconnecting feature formed on a terminal end thereof, the connectingfeature including anti-rotation features formed on a portion thereof; asecond spinal fixation rod angularly adjustable relative to the firstspinal fixation rod and having a connecting feature formed on a terminalend thereof, the connecting feature including anti-rotation featuresformed on a portion thereof; and a locking mechanism adapted to extendinto a bore formed in at least one of the first and second connectingfeatures and to translate at least one of the first and secondconnecting features toward the other one of the first and secondconnecting features to cause the anti-rotation features on the first andsecond connecting features to engage one another and maintain the firstand second spinal fixation rods in a fixed angular orientation relativeto one another.
 19. The spinal fixation device of claim 18, wherein theangular adjustability of each spinal fixation rod is limited to a singleplane.
 20. The spinal fixation device of claim 18, wherein the firstspinal fixation rod extends in a first plane, and the second spinalfixation rod extends in a second plane that is substantially parallel tothe first plane.
 21. The spinal fixation device of claim 18, furthercomprising a pin member adapted to removably couple the first and secondconnecting features.
 22. The spinal fixation device of claim 21, whereinthe locking mechanism extends along an axis that is substantiallyperpendicular to an axis of the pin member.